Description

Description. Test slightly pentagonal in outline (TL = 84 mm; TW = 79 mm), discoidal, fragile, with slight elevation in centre, ambitus extremely thin and sharp (Fig. 13 A – D). Apical system monobasal (Fig. 13 H), four gonopores (Fig. 13 H). Petaloid small, occupying only central region of test (Fig. 13 C, H). Posterior petals slightly longer than anterior ones (Fig. 13 A, C). Six long, slit-like lunules (Fig. 13 A – C), anal lunule shorter than five ambulacral ones (Fig. 13 A, C). Aboral primary spines strongly club-shaped, uniformly covering test (Fig. 13 A). Miliary spines with sac-like structure on tip, densely scattered among primary spines (Fig. 13 G). Lunules with two types of spines, on aboral margin, spines long, flat and slightly curved. Internally, spines are shorter, slenderer than aboral spines, but also slightly curved. Oral surface flat, with locomotory spines long, slender, and slightly curved at base, being largest spines in this region (Fig. 13 B). Short and slender spines occur among these spines. Spines on ambitus similar to those around lunules. Peristome circular and central (Fig. 13 B, D, E). Periproct small, elongate, close to peristome, slightly indenting basicoronal plate (Fig. 13 B, D). Basicoronal plates reduced in size. Ambulacral basicoronal plates almost triangular. Pressure drainage channels and food grooves well-developed (Fig. 13 D). Food grooves bifurcating after ambulacral basicoronal plates, surrounding lunules and reaching margin of test (Fig. 13 D). Pedicellariae. Pedicellariae over entire test, more abundant in oral inter and near the lunules, peristome, and periproct. Bidentate pedicellariae with a long neck (of same size or slightly smaller than the stalk) and short head. Valves short, with narrow and slightly curved base, median region enlarged with denticulate margin and two end teeth that cross with the teeth of opposing valve (Fig. 13 F). Colour. From yellow to brown or greenish (Hendler et al. 1995). Naked test white.

Common Names

Taxonomic Hierarchy

Kingdom: Animalia

Phylum: Echinodermata

Class: Echinoidea

Order: Echinolampadacea

Family: Mellitidae

Genus: Leodia

Species: Leodia sexiesperforata (Leske, 1778)